1. Field of the Invention
This invention pertains generally to liquid chromatography, and more particularly to apparatus for delivering samples of liquid to be analyzed in a chromatographic column.
2. Description of the Related Art
A number of different techniques have heretofore been employed for delivering liquid samples to chromatographic columns. In one such technique, the sample is placed in a syringe which is attached to a hollow metal needle. The sample is delivered to the column manually by piercing a septum with the metal needle and injecting the sample into the column.
U.S. Pat. No. 3,918,913 describes a system in which a stopper in a cylindrical container is pierced by a hollow metal needle which drives the stopper into the container in piston-like fashion, forcing the liquid sample out of the container through the opening in the needle.
These prior art systems have certain limitations and disadvantages. They all require a metal needle which pierces a seal in one form or another, and they may also require a separate metering stage to accurately control the amount of liquid delivered to the column. Even with metals of high quality, such as high alloy stainless steel, metal ions from the needle can be detected in the sample by the chromatographic instrument.
It is in general an object of the invention to provide new and improved apparatus for delivering a sample to a chromatographic column.
Another object of the invention is to provide apparatus of the above character which overcomes the foregoing and other limitations and disadvantages of the sample delivery systems heretofore provided.